bonjour
soient a la longueur et b la largeur
a + b = 72 : 2 = 36
a + b = 36 ⇒ a = 36 - b
ab = 315
( 36 - b ) b = 315
- b² + 36 b - 315 = 0
Δ = 36² - 4 ( - 1 * - 315 ) = 1 296 - 1 260 = 36 = 6 ²
x 1 = ( - 36 - 6 ) / - 2 = - 42/ - 2 = 21
x 2 = ( - 36 + 6 ) / - 2 = - 30/-2 = 15
dimensions = 21 par 1 5
P = 2 * 36 = 72
aire = 21 *15 = 315
